THE EFFECT OF SODIUM-CITRATE INGESTION ON THE METABOLIC RESPONSE TO INTENSE EXERCISE FOLLOWING DIET MANIPULATION IN MAN

Feeding a high-carbohydrate (CHO) diet;Ind administration of alkaliniz ing agents have both been shown to improve performance in high-intensi ty exercise. The effect of these treatments in combination was investi gated in the present study. Six healthy male subjects exercised to exh austion on an electrically braked cycle ergometer at a power output eq uivalent to 100% of their maximum oxygen uptake (V-O2,V-max) on four s eparate occasions. Each subject consumed either a diet with the same c omposition as his normal diet (termed the experimental normal (N) diet ; 54 +/- 7% CHO, 13 +/- 2% protein, 33 +/- 7% fat) or a high-CHO diet (81 +/- 2% CHO, 13 +/- 2% protein, 6 +/- 1% fat) that had the same ene rgy and protein content for the 3 days prior to the exercise tests. Su bjects then ingested either a placebo (CaCO3) or trisodium citrate (0. 3 g (kg body mass)(-1)) 3h before exercise. Time to fatigue was not di fferent between experimental conditions, Consumption of the high-CHO d iet had no effect on blood acid-base status, but the ingestion of sodi um citrate induced a mild metabolic alkalosis after both the N diet an d the high-CHO diet. This alkalinizing effect was also evident after e xercise, since blood pH, plasma bicarbonate and blood base excess were higher (P < 0.05) after the ingestion of sodium citrate than under th e placebo conditions. The changes in blood lactate, pyruvate and gluco se and plasma glycerol after exercise were similar for all experimenta l conditions. Blood lactate, glucose and pyruvate and plasma glycerol concentrations increased from resting values (P < 0.01) following exer cise but this increase was similar under all experimental conditions. These data demonstrate that when the energy and protein content of the diets is the same, exercise capacity and the metabolic response to in tense exercise are similar following consumption either of a high-CHO diet or a more normal diet. Acute ingestion of sodium citrate prior to exercise resulted in a reduction in post-exercise acidosis despite a blood lactate concentration that was similar to that observed after th e ingestion of a placebo, but did not affect exercise performance unde r the conditions of this study.